1. Field of the Invention
The present invention relates to a facilitated olefin transport membrane, and, more particularly, to a facilitated olefin transport membrane containing a polymer and a silver salt, which can stably maintain olefin separation performance for a long time by preventing the reduction of a silver salt.
2. Description of the Related Art
The present invention is a technology related to a composite membrane including: a polymer electrolyte layer containing a polymer, a silver salt and an aluminum salt; and a porous support film.
U.S. Pat. No. 6,468,331 discloses a technology related to a solid facilitated transport membrane having a selectivity of alkene (olefin)/alkane of 100 using a composite membrane including a polymer electrolyte layer containing a polymer and a metal salt and a porous support film. Further, U.S. Pat. No. 6,468,331 discloses a technology of selectively separating alkene-based hydrocarbons, wherein a polymer ligand and a metal cation are formed into a complex, and a double bond of alkene selectively or reversibly reacts with the metal cation of the complex to facilitate the transport of alkene, thus selectively separating alkene-based hydrocarbons.
However, the technology disclosed in U.S. Pat. No. 6,468,331 is problematic in that a silver salt is reduced to silver nanoparticles over time, and the reduction of a silver salt to silver nanoparticles deteriorates the performance of a facilitated transport membrane, and thus the facilitated transport membrane can no longer be used. In particular, AgBF4, which exists generally in the form of a free ion, is easily reduced to silver nanoparticles. Therefore, a technology for suppressing the reduction of a silver salt to silver nanoparticles is required.
Meanwhile, many investigations have been attempted to better understand the mechanism of silver ion reduction. For example, it was reported that N,N-dimethylformamide (DMF) in water facilitates the reduction of silver ions. Furthermore, it was reported that functional groups in a silver-polymer electrolyte exert a great influence on the reduction of silver ions in a facilitated olefin transport membrane. Recently, it was reported that the addition of additives such as dioctyl phthalate and HBF4 to a polymer/silver salt complex could be used to prevent silver ions from being reduced to silver nanoparticles. However, in these cases, there is a problem that a small amount of these additives should be added to a polymer/silver salt complex. Further, the reduction mechanism of silver ions with these additives is still unclear.